1. Field of the Invention
The present invention relates generally to agricultural harvesting machines with crop pick-up mechanisms and more particularly, is concerned with an improved system for counter-balancing the pick-up mechanisms of such machines.
The present invention has particular, but not exclusive, application to agricultural balers and has been conceived as an improvement over the baler disclosed and illustrated in U.S. Pat. No. 3,984,969. However, the invention has a wider application and may be embodied in any agricultural machine having a crop pick-up mechanism which term is intended to include the header of a combine harvester.
A baler typically comprises a mobile frame adapted to move across a field, means on the frame operable to receive crop material and form the material into bales, and a pick-up mechanism including pivot means on the frame and pick-up means disposed generally forwardly of the pivot means and operable to pick up crop material from the field and feed the material to the receiving and baling means. The pick-up means is connected to the pivot means for vertical swinging movement about the pivot means.
2. Description of the Prior Art
The prior art counterbalancing system disclosed in U.S. Pat. No. 3,984,969 includes a lever pivotally mounted on the frame for movement along a generally arcuate path about a generally horizontal pivot axis at a location above, and spaced from, one lateral side of the pick-up mechanism. The lever is pivotally arranged between a first, generally horizontally-extending position and another position at a substantial angle relative to the horizontal.
The counterbalancing means further include an elongated linkage interconnecting the pick-up mechanism at its one lateral side with the lever at a location spaced from its pivot, and resilient means mounted on the frame above the pick-up mechanism and acting upon the lever with a predetermined force adequate to counterbalance a substantial portion of the weight of the pick-up mechanism through the lever and interconnecting linkage and thereby floatingly to support the pick-up means in an operative position above the field.
The resilient means are disposed in relation to the pivot axis of the lever such that, during upward swinging movement of the pick-up mechanism about its pivot, which results in a generally upward movement of the lever along its arcuate path about its pivot axis, the moment arm of the counterbalancing force of the resilient means about the pivot axis of the lever increases as the magnitude of the counterbalancing force itself of the resilient means decreases. This tends to provide a substantially uniform flotation of the weight of the pick-up mechanism as it follows the contour of the field during movement of the baler across the field.
While this prior art system has, in an overall sense, proven to be a satisfactory way of counterbalancing the baler pick-up mechanism, some disadvantages have been discovered.
One disadvantage relates to the vertical displacement of the pick-up mechanism and the pivot lever. Both of these components move up and down in unison and over identically the same height. As it is desirable to have the pick-up mechanism capable of flotation over a large range of pick-up movement, this means that the lever should also be movable over a large range. This in turn means that, on the one hand, the lever has to be relatively long and, on the other hand, a large space has to be provided to accommodate pivotal movement of the lever. This space is not always available in all baler designs.
Another disadvantage derives from the fact that the resilient means are working close to the pivot axis of the pivot lever which means that heavy and expensive resilient means are required which, moreover, heavily load the pivot of the lever and cause substantial frictional forces thereon. These heavy frictional forces result in fast wear on the one hand and a less smooth flotation on the other hand.